The present invention relates to a method of making nap fabric strips for strip closure devices and to a strip-weaving machine for carrying out the method.
There are known closure devices comprising two strips, which possess on one side of each strip coupling means disposed in a laminar manner. One strip possesses knubs with deformed free ends. The free ends are either curved to a hook-shape or possess mushroom-shaped or club-shaped thickenings which act as barbs.
The method of making the strips hitherto has been first to weave a fabric possessing nap loops on a strip loom. To produce knubs with deformed free ends, the nap loops were then cut open on a second machine and deformed and stabilised by thermal treatment on a third machine. With this method of production, several machines were therefore necessary for the making of the strips. In addition, the transporting of the strips from the one to another machine naturally increased the amount of work.
From Swiss patent application No. 3854/73 is already now known a method which makes it possible to manufacture, in one operation on a single machine strips possessing knubs deformed to a mushroom shape. In this known method, two strips, extending in one section parallel to each other behind the edge of the fabric, are woven simultaneously. In the weaving, pile warp threads are introduced and woven in alternately into the basic weaves of each of the two strips in such a manner that they constitute connecting sections joining together the two basic weaves approximately perpendicularly to each other. The two weaves are heated up behind the edge of the fabric, in order that the pile warp filaments shall bond satisfactorily in the basic weave, and are then again cooled. Finally, the connecting sections are separated in the middle using a heated wire. By suitably selecting the temperature of the heated wire, the connecting sections are so melted during the cutting that mushroom-shaped, stable knubs are produced.
In this method, the strips possessing the deformed knubs, can, as already mentioned, be manufactured on one machine. This machine however, by comparison with weaving of strips without knubs, permits only a relatively low speed of weaving.
When the connecting sections are formed, the shed-forming device must transport the pile warp filaments from the shed of the one strip into the shed of the other strip during shed changing. This means that considerably longer pile warp thread sections are necessary than with those shed changes in which the pile warp threads are woven into the strips. In the forming of the connecting sections, the pile warp threads must therefore be fed to the shed-forming device at a higher speed than when weaving into the basic weave. In the already known method, the pile warp threads are stressed using a spring-loaded or weight-loaded thread tensioning device, in order to compensate the differing thread speeds between the warp beam or warp bobbins and the shed-forming device. It has however now been found that with a thread speed compensation of this type, only relatively low weaving speeds are possible, since otherwise uneven and unacceptably large thread tensions result. This disadvantage becomes further intensified by the fact that, in order to form the knubs, there ae normally used pile warp threads, which are of a different material from, and which possess a greater stiffness than, the basic warp and weft threads serving for forming the basic weave.
The stiffness of the pile warp threads necessitates, with the known method however, even where the pile warp threads are woven into the basic weave, a relatively low weaving speed, since otherwise relatively loose weaves result, in which the knubs are unsatisfactorily anchored.